What is a feature that indicates a high probability of arrhythmic syncope?

A feature that indicates a high probability of arrhythmic syncope is syncope while supine. This type of syncope often suggests a potential underlying cardiac issue, as arrhythmias can occur irrespective of position, including while lying down. Unlike other situations, such as syncope after eating or in warm environments, which may be more associated with vasovagal mechanisms or other non-cardiac causes, syncope while supine raises concern for serious arrhythmias that could lead to dangerous outcomes, especially in individuals with known heart problems.

Syncope during sleep can also be associated with cardiac issues but is less directly indicative of an arrhyhtmic event that occurs during activity or full alertness. Recognizing syncope while supine as a potential marker for arrhythmic syncope helps clinicians prioritize further investigation and management to ensure patient safety.